So this is scary. A retired fertility doctor from Indianapolis has been accused of using his own sperm to impregnate his patients over the course of his decades-long career.

People reports that Donald J. Cline, M.D., entered a plea of not guilty in Marion Superior Court to two counts of felony obstruction of justice related to the investigation.

Charges were filed because Dr. Cline apparently has a history of denying similar allegations to law enforcement. Most recently, Dr. Cline allegedly misled law enforcement officials in an ongoing investigation following complaints from two individuals claiming to have been fathered by Dr. Cline.

According to People, Dr. Cline operated a clinic in the 1970s, and over the course of eight years, he donated his own sperm over 50 times. The patients were told that the sperm was donated by medical and dental students.

At least three individuals who were fathered by Dr. Cline discovered their true parentage after taking DNA tests to explore their ancestry. One woman's DNA test revealed that she was related to eight people in a DNA database. Surprised, she contacted a local news station who helped to connect the family members and eventually determined that they are siblings.

Dr. Cline reportedly told his children that "he used his own sperm whenever he didn't have a donor sample available" when they confronted him about his actions.